1. The Field of the Invention
The present invention relates to catheters. In more particular, the present invention relates to an introducer sheath assembly having a reinforced dilator which minimizes kinking or bending of the dilator shaft.
2. The Relevant Technology
Catheters play an important role in the treatment and care of patients in modern medicine. In particular, catheters provide relatively unobtrusive access to remote portions of a patient's body, allowing desired procedures or treatments to be performed. A wide variety of generalized and specialized catheters have been developed and refined for particular uses. For example, angioplasty catheters have been adapted to provide a safe and effective conduit for the delivery of a stent and/or balloon to a narrowing or blockage in a patient's artery or vein. Typically, catheters are placed in a desired position within a patient utilizing a guidewire. The guidewire is threaded to the desired position within the patient and then the catheter is threaded over the guidewire.
One problem associated with some guidewires is that they have a diameter or thickness which requires a relatively large access puncture into the vasculature of the patient. The relatively large access puncture can result in damage to the artery or other patient tissue. Such damage can prolong the healing and/or bleeding time through the guidewire access point. Micropuncture catheters have been developed to provide a relatively smaller access puncture into the vasculature of the patient. Micropuncture introducer sheath assemblies include an introducer sheath which allows larger diameter guidewires to be introduced into the vasculature of the patient through the smaller access opening.
Utilizing a micropuncture introducer sheath assembly typically involves providing a small bore access puncture utilizing a small gauge needle. The needle is utilized to create an initial access puncture into the patient's vasculature. A small diameter guidewire is then threaded through the original puncture needle which has a smaller diameter than the guidewire which is to be utilized to guide the catheter to the desired location within the patient's vasculature. In one example, a guidewire having an 0.018″ diameter is utilized.
Once the micropuncture guidewire is positioned within the patient's vasculature, the original access needle can be withdrawn from the patient. An introducer sheath assembly is then threaded over the micropuncture guidewire. Typically, the catheter sheath has a somewhat resilient configuration which allows for desired operability in subsequent steps of the procedure. The dilator is positioned within the catheter sheath to provide additional rigidity required to insert the catheter sheath into the patient. Additionally, the dilator's tapered tip transitions from the guidewire's outer diameter to the diameter at the distal end of the sheath. The dilator typically includes a resilient dilator shaft which is sufficiently stiff to allow for access into the patient along the guidewire, but sufficiently resilient to prevent unneeded damage to the patient. Once the introducer sheath assembly has been introduced into the patient, the guidewire is withdrawn from the patient and subsequently the dilator is also withdrawn from the patient leaving the catheter sheath in place. A subsequent and larger diameter guidewire can then be introduced through the introducer sheath without the need to create a larger access puncture in the vasculature of the patient. Once the larger diameter guidewire is inserted into the patient, the catheter sheath can be withdrawn and the guidewire can be manipulated as required for proper placement of the guidewire in the patient's vasculature or within another position within the patient's body.
One problem that has been encountered with the use of such introducer sheath assemblies relates to introducer sheath assemblies that include a stiffener tube as part of the dilator. The transition between the stiffening tube and the tip of the dilator sometimes buckles or kinks during the insertion of the introducer sheath assembly into the patient. This is typically due to the fact that the stiffening tube that is positioned within the dilator has a greater rigidity and strength than the material from which the tip of the dilator is formed. As a result, multiple introducer sheath assemblies may need to be utilized during a single insertion procedure to allow for completion of the procedure once an initial dilator tip has failed. This can increase the time needed to complete the procedure, as well as cost due to the fact that multiple micropuncture catheters are utilized during the course of the procedure. A number of different approaches have been developed to attempt to strengthen dilators and dilator tips, however, such attempts can often be overly costly or fail to provide the desired properties to compensate for failure of such dilator tips.